It's really not much of a surprise, but it's nice to see these things in bar chart form every once in a while: AT&T drops many more calls than any other carrier.
A new survey by ChangeWave shows that 4.6% of of AT&T customers experienced a dropped call in the last 90 days, while only 1.8% of Verizon customers reported the same. When limited to just the iPhone, things are about the same, with 1.8% of Verizon iPhone customers dealing with dropped calls compared to 4.8% of AT&T's iPhone users.
But really, those numbers are both relatively low when we're talking about a single dropped call over a three month period. Verizon's is just lower.